Fatigue Life Of Aluminum Alloy Research Articles

116 アルミニウム合金ダイカスト高強度部品の疲労寿命予測法(各種特性・用途(2))

In aluminum alloy die castings under cyclic load, a fatigue crack initiates at casting defect and propagates according to Δ-da/dN relation. The prediction method of fatigue life of aluminum alloy die castings under complex cyclic load has been proposed theoretically and verified experimentally. The paper shows that the prediction method is a so effective to a part with complicated shape as well as a round bar specimen.

621 微粒子ピーニングによるアルミ鋳物の疲労強度向上

621 微粒子ピーニングによるアルミ鋳物の疲労強度向上

Investigation of the surface qualities of laser shock-processed zones and the effect on fatigue life of aluminum alloy

The influence of surface qualities produced by laser shock-processing (LSP) on the fatigue life of aluminum alloy 2024T62 are investigated. The surface qualities of LSP zones can be divided into grades A, B, C and D. The harmful heat damage produced by LSP is completely avoided in grade A surface quality, but heat damage exists to some extent in the others. Therefore, the grade A surface quality reflects the LSP contribution to fatigue life, which increases greatly. The main feature of grade A surface quality is that the surface roughness of the LSP zone is less than or equal to the surface roughness of the un-shocked zone. A very dense bright shallow hollow is formed and the shot spot is well-defined. With 95% confidence, the mean fatigue life of LSP specimens with grade A surface qualities is 4.8–8.1 times larger than the un-shocked ones.

Laser shock-processing for fatigue and fracture resistance

The generation mechanism of stress wave induced by laser-shocking is described and the stress wave is measured with a PVDF transducer. The visual inspections and control methods of the effectiveness of laser shock-processing (LSP) are built up. A small-sized, Q switched Nd: glass laser with high-power is used for LSP. The fatigue lives of aluminum alloy are increased greatly after LSP. With 95% confidence, the mean fatigue life of 2024T62 aluminum alloy after the LSP is 4.5–9.8 times that of the un-shocked ones. The hardness, microstructure and fracture section of materials are analysed before and after LSP. The anti-fatigue and anti-fracture mechanism is analysed and the prospects of wide applications of LSP, technology are described.

Influence of Fracture Mode Transition on Fatigue Life of Aluminum Alloy Reinforced by SiC Particles at Room and Elevated Temperatures.

A study has been made of the fatigue fracture mechanism in A6061 T6 metal matrix composite (MMC) reinforced with 5vol.% SiC particulate at room and elevated temperatures. The main results are summarized as follows. (1) Fatigue strengh decreased with increase of ambient temperature. (2) Relationship between fatigue life and temperature followed the Arrhenius rule. Therefore the fracture mechanism was the same, irrespective of ambient temperature. (3) Fatigue cracking of MMC initlated in the aluminum matrix and crack growth was in the shear mode, because the morphology of the fractured surface showed crystallographic facets. Then, fatigue crack growth mode changed from shear to monotonic fracture mode. (4) The transition occurred at the point at which the plastic zone size of the crack tip became larger than the average SiC particle size.

Finite-element prediction of high-cycle fatigue life of aluminium alloys: Baxter, W.J. and Wang, P.-C. Metall. Trans. A May 1990 21A, (5), 1151–1159

Finite-element prediction of high-cycle fatigue life of aluminium alloys: Baxter, W.J. and Wang, P.-C. Metall. Trans. A May 1990 21A, (5), 1151–1159

SEM study of humid air effect on fatigue of aluminum alloy 2024-T351

There is general agreement that the fatigue life of high strength aluminum alloys is reduced in humid environment. However, there are also data supporting the theory that humidity plays an insignificant role in the reduction of the fatigue life of aluminum alloy 2024-T351. In this study we examined the effects of stress level and water vapor density on the fatigue life of aluminum alloy 2024-T351 using scanning electron microscope (SEM). SEM evidence of the deleterious effect of humid air on the fatigue life of specimens cycled at intermediate stress level was presented. Discrepancies between this study and others were explained.Commercial aluminum alloy 2024-T35l (4.40Cu-1.45Mg-0.70Mn-0.23 Fe-0.15Si-0.13Zn) extruded bars were fatigue tested in reversed bending. The cycling was conducted in an environmentally controlled chamber. Ten specimens were machined for each fatigue stress level of 248, 276, 290, 317 and 359 MPa. Five specimens fran each stress level were cycled in desicated air at a relative humidity less than 45%.

Effect of stress cycle asymmetry on the fatigue life of aluminum alloys and the shape of their fatigue curves

1. The investigation produced fatigue curves for smooth specimens made from aluminum alloys D16T and AK4-1T1 at various stages of stress cycle asymmetry and the curves of equal fatigue life which makes possible an evaluation of the fatigue strength of the materials concerned for various combinations of variable and constant cycle load components. 2. It was established that the fatigue curves for investigated alloys have discontinuities at relatively low stresses commensurable with the proportionality limit, when the metal has no general plastic strain. 3. The position of discontinuities of fatigue curves in relation to the ordinate axis is not dependent on the degree of cycle asymmetry as long as the constant component of variable stresses has not reached a considerable magnitude. In this case the strain hardening produces microvolumes, where the fatigue processes are initiated and develop, a strengthening of the metal, and an increase in its yield strength which in turn increases the breaking stress on fatigue curves.